Manufacture of sensitive diazo-type layers



; May 31. 1932 Q uu rao sr TEs PATENT orricr DODIWLTIPIETEB MB VA!" DIR GBINTEN' AND RABBI. IAN JOSEPH VAN DEB GBIN'I'EN,

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. GM, 01 VENLO, TEERLANDSfA DUTCH COMPANY i macros: i

' DIAZO-TYPE LAYERS Io Drawing. Application fled Kay 1!, i880, Serial Io. 451,887, and in the Netherlands Kay 15, 1929.

It is known to make direct positive prints from positives by means of the diazo type process. It is also known that the development and fixing of the prints can take place in one action y simple addition of a substance (or' substances). ,7 This addition of substances can be efiected b treating the prints with agasor a liquid. 'I hetreatment with gasis limited to the ad- 16 ditionof alkali only,-and the sensitive layer must consequently contain the 'azo-component. In the case of treatment with liquid, this limitation does not exist, and the aper may contain only the. diazo compoun (in which case the developer contains alkali plus azo-component) or it may contain both com ponents (in which case the developer contains alkali but no azo-component) Each method (gas or liquid) has its advantages and dis.- dvantages.

Of-late, the liquid development has gained ound in practice, this method having been improved by U. S. Patents No. 1,841,653-and No. 1,821,306 and U. S. patent application 5 Serial No. 353,248. The treatment is rapid, simple and inodorous', and makes it posslble to apply reducing agents which prevent yellowing, but are not stable against acid, and also to apply a sizing agent with the developer. In the practice of the liquid method (since the introduction of the process according to U. S. Patent No. 1,841,653, also called the half wet method) the following difiiculty is encountered: 1

It is desirable that the developer shall have a simple composition. This might be obtained by incorporating the azo-component in the sensitive layer so that it can be omitted from the developer. According to the known processes in which this is effected, viz. that of U. S. Patent No. 1,444.469 or German Patent No. 422,972 or British Patent No. 234,818, the mixture of diazo compound and azo-component, forming the sensitive layer, must be a slowly reacting mixture, as otherwise coupling during storage before use cannot be prevented. According to the known processes coupling is prevented chiefly by using slow- 5o coupling (slightly active) diazo compounds,

such as diazo-anhydrides (vide U. S. Pat- I S, ASSIGNOBS '10 11'. V CHEMISCHE I'ABBIEK L. VAN DER No. 1,821,306, the difliculty is encountered that owing to the slowness of the cou ling reaction the separate substances of tlie layer dissolve in the liquid and spread more or less before the coupling is finished. The coupling is therefore complete oilly after this spreading has taken place, so that pigments are formed in the parts that have spread.

In this manner the pictures obtained are blurred, and in some cases have streaks in the background. This difiiculty is reduced to a minimum by the process according to U. S. Patent No. 1,841,653 and with the apparatus according to U. S. Patent No. 1,821,- 306, but only sufficiently for quick-coupling combinations, and not for the slow-coupling combinations of U. S. Patent No. 1,444,469,

German Patent No. 422,972 and British Patent No. 234,818.

These combinations can be developed with a very concentrated alkaline liquid, which promotes quick coupling by reason of its concentration, but in this case the support of the picture, the fibres and sizing of the paper are damaged, and the finished picture is liable to become very yellow. With these combinations the spreading of the colours can also be prevented to some extent by other more or less complicated 5 and detrimental means, for example by using developers which contain large quantities of salts, or developers in alcoholic solution.'. However, all these processes have considerable practical disadvantages.

As already stated, with quick-coupling combinations it is necessary, on account of the stability, to. apply both components separately, the dis zo-component being in the sensitive layer, and the azo-component being in the developer, so that these combinations are cswet development as above described, lightsensitive layers containing both components may be used, provided the layers are completely or approximately completely dried. Here it may be observed that normal dry ight-sensitive papers, including blue print paper, but more especially diazo-type papers for ammonia development, have a moisture content of about 6%. With diazo-type paper for gaseous development this moisture content is even a conditio sine qua non, as the paper would not couple or would couple'only very incompletely in gaseous ammonia if in a. perfectly dry condition.

The moisture content, with which the above mentioned quick-coupling combinations may be used in light-sensitivelayers containing both components, while maintaining a practically suflicient stability against coupling, is under 3-470. In practice, a moisture content of 12% can be reached, and a paper of very good stability is thus obtained.

As stated above, the combinations according to U. S. Patent No. 1,444,469, German Patent No. 422,972, British Patent No. 234,-- 818 and the patents corresponding therewith, are made too slow-coupling for gaseous development when they are prepared with a moisture content under 6%. Restoration of a. suflicient moisture content in order to obtain adequate development cannot take place,

or only insufliciently or in a very cumbrous manner. If a paper according to U. S. Patent No. 1,444,469, German Patent No. 422,972, British Patent No. 234.818 and the patents corresponding therewith has been wholly dried, the restoration of thecoupling velocity (development velocity) suflicient for gaseous development, necessitates a prolonged stay in a moist atmosphere, unless the moisture content is increased, for example by steam or the like, which is however too cumbrous for practical purposes.

The same difficulties are met when an at tempt is made to develop the above described strongly dried quick-coupling combinations with gases (although in a considerably aper has a moisture content of 5% or more.

later development is temporarily (during storage) taken away from this combination by maintaining a very low moisture content. On the other hand, even by the liquid development the substance water) is automatically supplied, which fa' ed for the posibility of coupling. Consequently, in the development of these layers not only the alkali is 'acti'v e, but also the water, which is indispensable for the reaction. These layers can be developed therefore practically only by water plus alkali, or in other words, only\ with an aqueous solution of alkali.

The stability of these layers, which consequently contain both substances of an actively coupling combination of diazoand amcomponents is, as explained above, due to the low moisture content. A characteristic feature of these layers is that even after one or several days, they show a detrimental deterioration (by premature coupling) if the moisin the form of water of crystallization, such as wholly or partly dehydrated aluminium sulphate or alum .or other salts, also substances acting on the 'azo-component, such as hvdroxylamine, semicarbazide and the like. However, these latter means have more or less the result of only displacing the diflieulty, as they hinder or delay the coupling in a manner which cannot be rectified by the developer with the same velocity as the absence of moisture. The reducing substances for preventing the yellowing of the diazo-types, de-

scribed in U. S. Patent No. 1,821,281 may.

also be added to the light-sensitive layers according to the invention. The addition of salts to the sensitive layers may further increase the sharpness of the pictures. The presence of salts which act as buffers to an alkali, such as ammonium salts. either in the sensitive layer or in the body of the support, diminishes the detrimental efi'ect of the alkaline developer on the sizing and the yellowing. Salts forming sparingly soluble compounds with the diazo compound, such as sodium chlorostannate, cadmium and zinc salts, increase the sharpness of the picture, as they better localize the diazo compound. Moreover, they have also a somewhat beneficial effect on the durability. as they influence favourably the localization and separation of the components, obtained by drying,

support, for example paper, before subjecting tothe intense drying. Owing to the intense drying according to this invention, the

paper (if prepared in this manner) becomes naturally brittle. This brittleness, however, is wholly or mainly removed by the half wet treatment on development. After this treatment the paper nearly regains its original tenacity.

Example 1 l a Paper containing an excess of alum is pretreated with a solution of 3% sodium chlorostannate, thereafter covered with a solution containing: 1% l-dibenzylamido benzene-4- diazonium chloride (prepared by diazotizing para dibenzylamido-aniline), 2% thiocarbamide, 1.2% hvdroxylamine sulphate, 5% glucose, 2% oxalic acid. 1% gelatine, 5% ammonium chloride, 0.2%phloroglucinol and 0.2% resorcinol.

After a short absorption the paper is intensively dried until the moisture content has fallen to about 2% (defined by loss of, Weight on completely dryinig at high temperature). This paper is sufiiciently stable for practical purposes, provided it remains completely drv. After exposure under a transparent original, the paper is developed in an apparatus according to U. S. Patent No. 1.821.306 with a solution of 3 sodium carbonate. 5% sodium thiosulphate and 5% sodium Citrate.

A strong positive image on a white ground is obtained which ground does'not become yellow. It is also possible to use ordinary paper and to omit the pretreatment. The paper is then somewhat less stable and the prints become a little more yellow. Also the thiocarbamide and glucose mav be left out of the layer. and the thiosulnhate and citrate may be left out of thedeveloper, resulting.

however, in yellowing. If the hvdroxylamine and oxalic acid are omitted the paper becomes somewhat less stable, but in that case Paper is brushed on the back with a 10% solution of ammonium chloride, and then on the front with a solution containing: 1% 1- di-isoamylamine benzene-4-diazonium chlorostannate (prepared by diazotizing paradi-isoamylaniline and adding tin chloride Paper is covered with a solution of: 2% 3 diazo hexahydrocarbazol -chlorostannate (prepared by diazotizing 3 amino hexahydrocarbazol and addin tin chloride in strong hydrochloric acid 2% thiocarbamide, 2% hydroxylamine sulphate, 1% semicarbazide chloride, 2% tartaric acid, 5%

sodium citrate, 5% sodium chloride, 0.2% phloroglucinol.

The paper is intensively dried until the moisture content has fallen below 2%. The

paper is of a scarcely. suflicient stability. After exposure the paper isdeveloped as describedin Example 1 with a solution of 2% soda, 10% sodium thiosulphate. v

The development can also take place with a bicarbonate solution, sodium borate and the like. A strong positive picture is obtained. Certain substances may be omitted as described in Example 1.

If the citrate and'sodium chloride are omitted from the layer, somewhat less sharp pictures are obtained.

What we claim is v 1. The process for preparing a base having a light sensitive diazo type layer thereon which comprises applying a rapidly coupling mixture of a diazo compound and an azo dyestuff component to said base, and drying the base until the moisture content thereof is reduced to a point not exceeding 1% of its dry weight. '2. The process according to claim 1 whereand strong hydrochloric acid), 2% tfiim". .bamide, 2%

in the diazo compound is a dia'zochlorostanna'te.

3. The process for preparing a base having a light sensitive diazo type layer thereon which comprises applying a buffering agent and a rapidly coupling mixture of a diazo compound and an azo dyestuif component to'said base, and drying the base until the moisture content thereof is reduced to a point not exceeding 4% of its dry weight.

4. The process according to claim 3 where: in the buffering agent is an ammonium salt.

5. The process according to claim 3 wherein the diazo compound is a diazochlorostannate.

6. The process for preparing a base having a light sensitive diazo type layer thereon which comprises applyinga rapidly coupling mixture comprising a diazo compound, an azo dyestufi component, and a substance capable of arresting the coupling activity of sa d mixture to said base, and drying the base until the moisture contentthereof is reduced to a point not exceeding of its dry weight. 7. The process accordlng to claim 6 wherein the substance is an acidic substance.

,8. The process according to claim 6 wherein the substance is a salt capable of combining with water in the form of water of crystallization.

9. The process according to claim 6 wherein the substance is hydroxylamine.

10. The process according to claim 6 Wherein the diazo compound is a diazochlorostannate.

11. The process for preparing a base having a light sensitive diazo type layer thereon which comprises applying a rapidly coupling mixture comprising a diazo compound, an azo dyestufi component,- and a reduc ng agent capable of arresting the discoloratlon of the background of the finished print, and drying the base until the moisture content thereof is reduced to a point not exceeding 4% of its dry weight.

12. The process according to claim 11 wherein the diazo compound is a diazochlorostannate.

13. The process for preparing a base having a light sensitive diazo type layer thereon which comprises applying a rapidly coupling mixture comprising a diazo compound, an azo dyestufi component, and a salt capable of forming with said diazo compound a difli cultly soluble salt, and drying the base until the moisture content thereof is reduced to a point not exceeding 4% of its dry weight.

14. The process according to claim 13 wherein the diazo compound is a diazochlorostannate.

15. As a new product, a base having thereon a sensitive layer comprising a rapidly couplin mixture of a diazo compound and an azo dyestuif component, said base having the moisture content reduced to a point not exceeding 4% of its dry weight.

16. As a new product, a base having thereon a sensitive layer comprising a rapidly coupling mixture of a diazo compound and an azo dyestufi component, said base having its moisture content reduced to less than 8% of its dry weight.

17. As a new product, a base having a sonsitlve layer comprising a bufli'ermg agent and a rapldly coupling mixture of a dlazo compound and an azo dyestufl' component thereon, said base having the moisture content reduced to a point not exceeding 4% of its dry weight.

18. As anew product, a base having a sensitive layer comprising a rapidly coupling mixture of a diazo compound and an azo dyestufi component and a substance capable of moisture content thereof is reduced to 1,ae1,aso

reduced to a point not exceeding 4% of its dry wei ht.

19. T e product according to claim 18 wherein the substance is an acidic substance. 20. The product according to claim 18 wherein the substance is hydroxylamine.

21. As a new product, a base having thereon a sensitive layer comprising a rapidly couplin mixture of a diazo compound and an azo dyestufi component and a salt capable of formin with said diazo compound a diflicultly solu le salt, said base having the moisture content reduced to a point not exceeding 4% of its dr weight.

22. The pro uct according to claim 21 wherein the diazo compound is a dia zochlorostannate.

v 23. A process for preparing a base having a light sensitive dlazotype layer thereon, which comprises impregnating the base with a buffering agent and applying a rapidly coupling mixture of a diazo compound and an azo dyestufi component to the surface of said base, and drying the base until the moisture content thereof is reduced to a point not exceeding 4% of its dry weight.

' 2 4. A process for preparing a base having a light sensitive diazotype layer thereon, which comprisesimpre nating the base with an acidic substance and-applying a rapidly coupling mixture of a diazo compound and an azo dyestuif component to the surface of said base, and drying the base until the not exceeding 4% of its dry weight.

25.- A process for preparing a base having a light sensitive diazotype lay'er. thereon, which comprises impregnating the base with a salt capable of arresting bleeding of the print upon contact with the developmentliquid, and applying a rapidly coupling mixture of a diazo compound and an azo dyestufi' component to the surface of said base, and drying the base until the moisture content thereof is reduced to a point not exceeding 4% of its dry weight.

26. A process for preparing a base having a light sensitive diazotype layer thereon, which comprises impregnating the base with a salt capable of forming upon reaction with a diazo compound a diflicultly soluble compound, and applying a rapidly coupling mix a point 

